News Feature | June 17, 2014

Reverse Osmosis: Expensive, Inefficient, Obsolete?

Emerging technologies may replace reverse osmosis and provide a more cost-effective approach to desalination, according to a survey of new equipment published this month in the journal Yale Environment 360.

There are two big problems with reverse osmosis technology: It is not cheap or environmentally-friendly.

"The current standard technology, reverse osmosis — in which high-pressure pumps force water through semi-permeable membranes to exclude salt and impurities — uses large amounts of energy and has an outsized impact on the environment. These effects include damage to aquatic ecosystems, such as sucking in fish eggs with its intake water; using harsh chemicals to clean membranes; and releasing large volumes of highly salty liquid brine back into the water," the report said.

That's a big problem in environmentally-conscious California, where a severe drought has dragged on for years. “Desalination is a really hot button issue in California — a lot of people oppose it,” said Aaron Mandell, co-founder and chairman of Water FX, in the report.

The cost of operating desalination equipment is often prohibitive. "Costs vary, but the lowest price for desalinated seawater from a reverse osmosis plant is around $750 an acre-foot (325,851 gallons) — more than double the average cost of groundwater," the report said.

Inventors are scrambling to find a more efficient method.

"Engineers and entrepreneurs across the globe are now trying to devise greener desalination. Some are inventing new alternatives to traditional reverse osmosis," the report said.

So, which technologies show the most promise?

Solar desalination is among the most high-profile options. Check out Water Online's report on Mandell's solar desalination efforts.

Gizmodosummarized other alternatives: "There's a [host of] ideas hatching out of labs: 'porous carbon aerogel electrodes' that remove salt electrically, nanotechnology that prevents bacteria biofilms from clogging up filtration membranes, a 'plant in a box,'" it reported.

Graphene is another key alternative.

"One of the hottest new technologies on the bench in laboratories in the U.K., Saudi Arabia, and South Korea and elsewhere is one-atom thick, perforated graphene membranes that can cut reverse osmosis desalination to a fraction of its current cost. Developed at the Massachusetts Institute of Technology, the membrane’s pores can be tuned to optimize permeability. The hang-up for now is how to mass-produce the material," the Yale report said.

In spite of compelling alternatives, reverse osmosis is expected to maintain its dominance in the desalination market. "For urban water needs, even those working on alternative methods say reverse osmosis (RO) will likely remain the top choice for the foreseeable future," the report noted.

Israel is one country that has made major investments in desalination technology, and experts say it is paying off.

"After experiencing its driest winter on record, Israel is responding as never before — by doing nothing," the Associated Press recently reported.

"While previous droughts have been accompanied by impassioned public service advertisements to conserve, this time around it has been greeted with a shrug — thanks in large part to an aggressive desalination program that has transformed this perennially parched land into perhaps the most well-hydrated country in the region," the report said.